Antimicrobial actions of lactoferrin

A nutritional supplement containing lactoferrin stimulates the immune system, extends lifespan, and reduces amyloid β peptide toxicity in Caenorhabditis elegans

Lactoferrin is a highly multifunctional glycoprotein involved in many physiological functions, including regulation of iron absorption and immune responses. Moreover, there is increasing evidence for neuroprotective effects of lactoferrin. We used Caenorhabditis elegans as a model to test the protective effects, both on phenotype and transcriptome, of a nutraceutical product based on lactoferrin liposomes. In a dose‐dependent manner, the lactoferrin‐based product protected against acute oxidative stress and extended lifespan of C. elegans N2. Furthermore, Paralysis of the transgenic C. elegans strain CL4176, caused by Aβ1‐42 aggregates, was clearly ameliorated by treatment. Transcriptome analysis in treated nematodes indicated immune system stimulation, together with enhancement of processes involved in the oxidative stress response. The lactoferrin‐based product also improved the protein homeostasis processes, cellular adhesion processes, and neurogenesis in the nematode. In summary, the tested product exerts protection against aging and neurodegeneration, modulating processes involved in oxidative stress response, protein homeostasis, synaptic function, and xenobiotic metabolism. This lactoferrin‐based product is also able to stimulate the immune system, as well as improving reproductive status and energy metabolism. These findings suggest that oral supplementation with this lactoferrin‐based product could improve the immune system and antioxidant capacity. Further studies to understand the molecular mechanisms related with neuronal function would be of interest.

Antimicrobial Peptides in Human Sepsis

Nearly 100 years ago, antimicrobial peptides (AMPs) were identified as an important part of innate immunity. They exist in species from bacteria to mammals and can be isolated in body fluids and on surfaces constitutively or induced by inflammation. Defensins have anti-bacterial effects against Gram-positive and Gram-negative bacteria as well as anti-viral and anti-yeast effects. Human neutrophil peptides (HNP) 1-3 and human beta-defensins (HBDs) 1-3 are some of the most important defensins in humans. Recent studies have demonstrated higher levels of HNP 1-3 and HBD-2 in sepsis. The bactericidal/permeability-increasing protein (BPI) attenuates local inflammatory response and decreases systemic toxicity of endotoxins. Moreover, BPI might reflect the severity of organ dysfunction in sepsis. Elevated plasma lactoferrin is detected in patients with organ failure. HNP 1-3, lactoferrin, BPI, and heparin-binding protein are increased in sepsis. Human lactoferrin peptide 1-11 (hLF 1-11) possesses antimicrobial activity and modulates inflammation. The recombinant form of lactoferrin [talactoferrin alpha (TLF)] has been shown to decrease mortality in critically ill patients. A phase II/III study with TLF in sepsis did not confirm this result. The growing number of multiresistant bacteria is an ongoing problem in sepsis therapy. Furthermore, antibiotics are known to promote the liberation of pro-inflammatory cell components and thus augment the severity of sepsis. Compared to antibiotics, AMPs kill bacteria but also neutralize pathogenic factors such as lipopolysaccharide. The obstacle to applying naturally occurring AMPs is their high nephro- and neurotoxicity. Therefore, the challenge is to develop peptides to treat septic patients effectively without causing harm. This overview focuses on natural and synthetic AMPs in human and experimental sepsis and their potential to provide significant improvements in the treatment of critically ill with severe infections.

Preparation and antimicrobial action of three tryptic digested functional molecules of bovine lactoferrin

Lactoferrin is an 80 kDa bilobal, iron binding glycoprotein which is primarily antimicrobial in nature. The hydrolysis of lactoferrin by various proteases in the gut produces several functional fragments of lactoferrin which have varying molecular sizes and properties. Here, bovine lactoferrin has been hydrolyzed by trypsin, the major enzyme present in the gut, to produce three functional molecules of sizes approximately 21 kDa, 38 kDa and 45 kDa. The molecules have been purified using ion exchange and gel filtration chromatography and identified using N-terminal sequencing, which reveals that while the 21 kDa molecule corresponds to the N2 domain (21LF), the 38 kDa represents the whole C-lobe (38LF) and the 45 kDa is a portion of N1 domain of N-lobe attached to the C-lobe (45LF). The iron binding and release properties of 21LF, 38LF and 45LF have been studied and compared. The sequence and structure analysis of the portions of the excision sites of LF from various species have been done. The antibacterial properties of these three molecules against bacterial strains, Streptococcus pyogenes, Escherichia coli, Yersinia enterocolitica and Listeria monocytogenes were investigated. The antifungal action of the molecules was also evaluated against Candida albicans. This is the first report on the antimicrobial actions of the trypsin cleaved functional molecules of lactoferrin from any species.

Supplementation transgenic cow's milk containing recombinant human lactoferrin enhances systematic and intestinal immune responses in piglets

Lactoferrin (LF) plays an important role in the body's immune system. However, the immunomodulatory effects of supplementation transgenic cow's milk containing recombinant human LF (rhLF) on the systemic and intestinal immune systems in infants remain unclear. Our laboratory has used genetic engineer to produce transgenic cow secreted rhLF. To assess the immune responses we took piglets as an animal model for infants. Eighteen piglets at 7 days of age were fed ordinary milk, 1:1 mix of ordinary and rhLF milk, or rhLF milk (LFM) for 30 days. The incidence of diarrhea in piglets in natural condition was observed. The protein abundances of immunoglobulin (Ig)G, IgA, IgM, IgE, histamine, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-8, IL-10, IL-12 interferon, tumor necrosis factor in the plasma, spleen or intestine were measured by enzyme-linked immunosorbent assay. Intestinal structure was assessed by hematoxylin and eosin. The mRNA levels of immune and allergy-related genes were measured by quantitative reverse transcription-polymerase chain reaction. The results showed that LFM-fed significantly reduced incidence of diarrhea, enhanced humoral immunity, T helper (Th) 1, and Th2 cell responses, improved the structure of the intestinal mucosal and did not induce food allergy. LFM increased mRNA levels of toll-like receptor 2 and nuclear factor-κB p65 and decreased that of FCεRI β. In conclusion, rhLF-enriched formula could improve systematic and intestinal immune responses and did not elicit food allergies in neonatal piglets.

Antimicrobial lactoferrin peptides: the hidden players in the protective function of a multifunctional protein

Lactoferrin is a multifunctional, iron-binding glycoprotein which displays a wide array of modes of action to execute its primary antimicrobial function. It contains various antimicrobial peptides which are released upon its hydrolysis by proteases. These peptides display a similarity with the antimicrobial cationic peptides found in nature. In the current scenario of increasing resistance to antibiotics, there is a need for the discovery of novel antimicrobial drugs. In this context, the structural and functional perspectives on some of the antimicrobial peptides found in N-lobe of lactoferrin have been reviewed. This paper provides the comparison of lactoferrin peptides with other antimicrobial peptides found in nature as well as interspecies comparison of the structural properties of these peptides within the native lactoferrin.

Effects of orally administered lactoferrin and lactoperoxidase-containing tablets on clinical and bacteriological profiles in chronic periodontitis patients

This study was undertaken to evaluate the effect of oral administration of lactoferrin (LF) and lactoperoxidase-(LPO-)containing tablet on periodontal condition. Seventy-two individuals with chronic periodontitis were randomly assigned to take either bovine LF and LPO-containing tablets (test group, n = 37) or control tablets (control group, n = 35) every day for 12 weeks. Periodontal parameters and levels of subgingival plaque bacteria, human and bovine LF, and endotoxin in gingival crevicular fluid (GCF) were evaluated at baseline, 1 week, 4 weeks, and 12 weeks. Significant differences were observed in GCF levels of bovine LF between the test and control groups throughout the study (P < .05). However, clinical and bacteriological parameter values proved comparable between the two groups at 1 week to 12 weeks. Therefore, the effect of oral administration of LF and LPO-containing tablets might be weak on periodontal and bacteriological profile in this study.

Inhibitory effects of lactoferrin on growth and biofilm formation of Porphyromonas gingivalis and Prevotella intermedia

Lactoferrin (LF) is an iron-binding antimicrobial protein present in saliva and gingival crevicular fluids, and it is possibly associated with host defense against oral pathogens, including periodontopathic bacteria. In the present study, we evaluated the in vitro effects of LF-related agents on the growth and biofilm formation of two periodontopathic bacteria, Porphyromonas gingivalis and Prevotella intermedia, which reside as biofilms in the subgingival plaque. The planktonic growth of P. gingivalis and P. intermedia was suppressed for up to 5 h by incubation with >or=130 microg/ml of human LF (hLF), iron-free and iron-saturated bovine LF (apo-bLF and holo-bLF, respectively), and >or=6 microg/ml of bLF-derived antimicrobial peptide lactoferricin B (LFcin B); but those effects were weak after 8 h. The biofilm formation of P. gingivalis and P. intermedia over 24 h was effectively inhibited by lower concentrations (>or=8 microg/ml) of various iron-bound forms (the apo, native, and holo forms) of bLF and hLF but not LFcin B. A preformed biofilm of P. gingivalis and P. intermedia was also reduced by incubation with various iron-bound bLFs, hLF, and LFcin B for 5 h. In an examination of the effectiveness of native bLF when it was used in combination with four antibiotics, it was found that treatment with ciprofloxacin, clarithromycin, and minocycline in combination with native bLF for 24 h reduced the amount of a preformed biofilm of P. gingivalis compared with the level of reduction achieved with each agent alone. These results demonstrate the antibiofilm activity of LF with lower iron dependency against P. gingivalis and P. intermedia and the potential usefulness of LF for the prevention and treatment of periodontal diseases and as adjunct therapy for periodontal diseases.

Bovine lactoferrin stimulates anchorage-independent cell growth via membrane-associated chondroitin sulfate and heparan sulfate proteoglycans in PC12 cells

Bovine lactoferrin (bLf) is an iron-binding secretory protein present in breast milk, mucosal secretions, and the secondary granules of neutrophils. Although bLf has multiple functions, including antimicrobial and immunomodulatory activities, its effect on neuronal cells is not fully understood. We report that bLf prevents cell adhesion of PC12 cells and allows them to be cultivated in suspension. PC12 cells normally adhere well to plastic culture plates and show anchorage-dependent cell growth, but we found that soon after adding bLf, they detach from culture plates and begin to grow in suspension. When bLf was removed from the medium, the cells began to re-adhere to the plates. Thus, bLf inhibits cell adhesion and stimulates anchorage-independent growth in PC12 cells. On the other hand, bLf-induced cell suspension growth was not observed when cells were grown on a laminin matrix, suggesting that bLf does not affect integrin-mediated cell adhesion on a laminin matrix. Treatment of cells with heparin or chondroitin sulfate A or C inhibited bLf-induced growth in cell suspension. Furthermore, pretreatment of cells with heparinase and/or chondroitinase prevented direct binding of bLf to the cell membrane. These results suggest that bLf binds to the membrane of PC12 cells via membrane-associated proteoglycans and leads to anchorage-independent growth.

Modulation of immunity-related gene expression in small intestines of mice by oral administration of lactoferrin

Oral administration of lactoferrin (LF), an antimicrobial and immunomodulatory protein, shows a protective effect against infectious diseases, possibly via immunomodulation of the host. Initially, we confirmed an immunomodulatory effect of LF by observing changes in the number of cells in the leukocyte subsets in the peripheral blood and spleens of mice 1 day after oral administration of LF. Then we developed a quantitative reverse transcription-PCR method for 20 immunity-related genes of antimicrobial proteins, pattern recognition receptors, cytokines, and lymphocyte mobilization-related proteins, and we assessed the expression of these genes in the small intestines of mice 2 h after administration of water, bovine serum albumin (BSA), or LF. Expression of the LF gene was lower in mice administered LF than in mice administered water or BSA, implying a negative-feedback control. Expression of gamma interferon (IFN-gamma) and interleukin-10 (IL-10) was lower in both BSA- and LF-administered mice than in water administered mice, suggesting a nonspecific effect of protein ingestion. Expression of NOD2, IFN-beta, and IL-12p40 was higher with LF administration than with water or BSA administration. The expression levels of these three genes were correlated. This study indicated that oral administration of LF modulates the small intestinal expression of genes closely related to the host defense in a specific or a nonspecific manner.